So there was this:
And I bought this:
And @professor provided a testing plan. So this is really his results. I was just the errand boy, the technician who ran the tests. And supposedly the results are interesting. So here they are.
Equipment:
iPad Pro 11 (2018). Battery capacity of 29.45 Wh.
Anker PowerCore Essential 20000 PD. Battery capacity of 72Wh.
Klein meter shown above.
15V Test:
- Depleted my iPad to 0% (shut down on its own).
- Used the PowerCore to recharge the iPad (USB-C PD at 15V).
- Depleted my iPad to 0% again.
- Used the PowerCore to recharge the iPad (USB-C PD at 15V).
5V Test:
- Depleted my iPad to 3%.
- Used the PowerCore to recharge the iPad (USB-A at 5V).
- Repeat until PowerCore was depleted.
15V Result:
- The meter measured 67.54 Wh from the battery (72 Wh) = 93.8% PowerCore efficiency.
- The iPad was recharged 1.83 times. (29.45 x 1.83) / 67.54 = 79.8% iPad battery efficiency.
5V Result:
- The meter measured 69.49 Wh from the battery (72 Wh) = 96.5% PowerCore efficiency.
- The iPad was recharged 1.96 times. (29.45 x 1.96) / 69.49 = 83.1% iPad battery efficiency.
NOTE:
- I had several cables to choose from. @professor provided guidance in choosing the most efficient cable to run these tests.
- For both 15V and 5V tests, the iPad charged rapidly until around the 80% mark, then it gradually slowed down (same voltage but lower amps) as the iPad approached 100%.
- The Klein meter is not that great. I had to set up a webcam to capture what was going on: when the test ended, the total Wh used, etc. I usually unplugged 30-90 minutes past the end of test. After iPad reached 100%, <0.05 Wh was consumed for trickle charging for each test run.
- For the 5V test, I had to start the iPad at 3%. When it was 0%, the iPad would not recharge. Maybe it was because of the meter in the middle? Not sure, but at 0% and even at 1%, the iPad would not recharge. This is why I started at 3%.
If you have technical questions, then @professor can answer them.
If you have questions about the setup, then we may both be able to answer them.